Cavity Ring Down Spectroscopy Technology

Knowledge Introduction

     Cavity ring down spectroscopy technology is a emerging method of spectrum detection. The technology is especially suitable for trace absorption of substance with its characteristics of long absorption optical path and unaffected by the change of light intensity. It is applied to the accurate measurement of high reflectivity of lens (accuracy up to 10^-4 ～10^-6) and trace gas detection because of simple device and easy quantitative measurement.

        As shown in the fig 1, optical resonant cavity composed of high reflectivity lens M1 and M2, when the 532nm pulsed laser along the optical axis is injected into the cavity, the laser pulse is reflected back and fourth between the two mirrors and from oscillation. Ringdown process of laser pulse in the cavity is detected by the photodetector behind M2 and ringdown time is recorded. Then the reflectivity of lens can be calculated out according to the ringdown time. The students can learn the method to measure the reflectivity of lens accurately by the experiment.

Experiment Device

       Main points:

       a) The principle of cavity ring down spectroscopy technology

       b) The characteristics and application of cavity ring down spectroscopy technology

       c) Lens reflectivity of straight cavity measurement with cavity ring down spectroscopy technology

       d) The choice of core components of cavity ring down spectroscopy technology

Experiment result

·Lens reflectivity of folded cavity measurement

·The content of the gas detection

·Observation and analysis of laser modes based on plane scanning interferometer

·Teaching experiment and research applications

·Lens with high reflectivity measurement

·The concentration of trace gases detection